A rotary electric machine is mounted on an electric vehicle or the like. The rotary electric machine has heat sources such as a coil disposed in a stator and a permanent magnet disposed in a rotor that generates heat by operation, so that those need to be cooled. For example, JP-A-2014-64433 discloses that a guide groove is formed to extend spirally on an inner wall surface of a hollow rotor shaft and a coolant supplied to the inside of the rotor shaft is guided to a through hole formed radially in the rotor shaft by the operation of the rotating guide groove such that the flow rate of the delivered coolant is secured.
According to the rotor shaft of the rotary electric machine disclosed in JP-A-2014-64433, it is necessary to form the spiral guide groove on the inner wall surface of the hollow rotor shaft, and thus there is a concern that the rigidity of the rotor shaft decreases.